Thermal treatment equipment and method for heat-treating

ABSTRACT

The invention provides a method for activating impurity element added to a semiconductor and performing gettering process in shirt time, and a thermal treatment equipment enabling to perform such the heat-treating. The thermal treatment equipment comprises treatment rooms of n pieces (n&gt;2) performing heat-treating, a preparatory heating room, and a cooling room, and heating a substrate using gas heated by heating units of n pieces as a heating source, wherein a gas-supplying unit is connected to a gas charge port of the cooling room, a discharge port of the cooling room is connected to a first gas-heating unit through a heat exchanger, a charge port of an m-th (1≦m≦(n−1)) treatment room is connected to a discharge port of an m-th gas-heating unit, a charge port of an n-th treatment room is connected to a discharge port of an n-th gas-heating unit, a discharge port of the n-th treatment room is connected to the heat exchanger, and discharge port of the heat exchanger is connected to gas charge port of the preparatory heating room.

This application is a divisional of application Ser. No. 10/706,357filed on Nov. 12, 2003 now U.S. Pat. No. 7,022,589 which is a divisionalof prior application Ser. No. 10/156,873 filed on May 29, 2002 (now U.S.Pat. No. 6,649,544 issued Nov. 18, 2003).

BACKGROUND OF THE INVENTION

The present invention relates to a method for heat treating and athermal treatment equipment applying the method. Particularly, theinvention relates to the thermal treatment equipment heating a substrateor a formed matter on the substrate by heated gas and the method forheat-treating using the equipment.

In a manufacturing process of a semiconductor device, thermal treatmentsaiming at oxidation, diffusion, gettering, and recrystallization afterion injection with respect to a semiconductor or a semiconductorsubstrate are programmed. A typical example of the equipment performingthese thermal treatments is a hot wall type annealing furnace ofhorizontal type or vertical type, which is used widely.

The annealing furnace of horizontal type or vertical type is batch typeequipment treating many substrates in a lump. For example, the verticalannealing furnace mounts a substrate on a suscepter formed by quartzhorizontally and in parallel, and performs putting in and out to areaction pipe by an elevator driving up and down. At outer circumferenceportion of a bell-jar type reaction pipe, a heater is provided so as toheat a substrate by the heater. It takes comparatively long time forrising time reaching the predetermined heating temperature and fallingtime cooling to temperature possible to take out because of theconstruction thereof.

Incidentally, in MOS transistor used for an integrated circuit, veryhigh process accuracy is required as elements become fine. Especially,it needs to diffuse impurity at the minimum for forming thin junction.However, process taking long time for rising temperature and fallingtemperature as the annealing furnace makes forming thin junctiondifficult.

Rapid thermal anneal (described RTA hereafter) method is developed asthermal treatment technique performing rapid heating and rapid cooling.An RTA equipment heats a substrate or a formed matter on the substraterapidly using infrared ray lamp so as to perform thermal treatment inshort time.

A thin film transistor (described TFT hereafter) is well known asanother form of a transistor.

The TFT is paid attention as technique possible to form an integratedcircuit directly on a glass substrate. The technique is advanced forapplication development for new electronic device such as a liquidcrystal display device. Especially, the FET forming impurity domainssuch as a source domain and a drain domain on a polycrystalsemiconductor film formed on the glass substrate needs thermal treatmentfor activating and easing of distortion. However, the glass substratehas demerits that distortion point thereof is only 600 to 700° C. and itis broken easily by thermal shock.

In the vertical or horizontal type annealing furnace of the related art,it becomes difficult to obtain uniformity of heating temperature whensize of the substrate is large regardless of whether substrate formingthe integrated circuit is semiconductor or insulation material such asglass or ceramic. In order to obtain uniformity of temperature insubstrate surface and between substrates, it needs to make pitch oftreated substrate mounting horizontally and in parallel wide because ofcharacteristic of gas flowing in the reaction pipe as fluid. Forexample, when a side of the substrate exceeds 500 mm, pitch of thesubstrate is necessary to take more than 30 mm.

Therefore, as the treated substrate is large, the equipment isnecessarily large size. Because many substrates are treated in a lump,weight of substrates themselves increases, and suscepter mounting thetreated substrate needs strength. Because of that, the weight increases,and operation of the machine carrying in and out the treated substratebecomes slow. Further, the instrument influences not only to increase offloor area occupied by the thermal treatment equipment but also tobuilding cost for a building having withstand load of the floor. Thus,large sized equipment forms a vicious circle.

On the other hand, the RTA method processes piece by piece as premise sothat load of the equipment does not increase extremely. However,difference in absorptance of lamp of light used for heating unitgenerates because of characteristic of the treated substrate and theformed matter thereon. For example, when a pattern of metal wiring isformed on the glass substrate, a phenomenon that the metal wiring isheated earlier and the glass substrate is broken by local distortiongenerates. Because of that, complex control such as adjusting risingspeed is required.

The invention is aimed at solution of the problem, that is, the objectof the invention is to provide a method activating impurity elementadded to semiconductor by short time thermal treatment and performinggettering process, and a thermal treatment equipment possible to performsuch the thermal treatment.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problem, A construction of thermaltreatment equipment of the invention comprises treatment rooms of npieces (n>2) performing heat-treating, a preparatory heating room, and acooling room, and heating a substrate using gas heated by heating unitsof n pieces as a heating source, wherein a gas-supplying unit isconnected to a gas charge port of the cooling room, a discharge port ofthe cooling room is connected to a first gas-heating unit through a heatexchanger, a charge port of an m-th (1≦m≦(n−1)) treatment room isconnected to a discharge port of an m-th gas-heating unit, a charge portof an n-th treatment room is connected to a discharge port of an n-thgas-heating unit, a discharge port of the n-th treatment room isconnected to the heat exchanger, and a discharge port of the heatexchanger is connected to a gas charge port of the preparatory heatingroom.

Number of the treatment rooms connecting with gas pipes is option. Thatis, another construction of thermal treatment equipment of the inventioncomprises treatment rooms and gas-heating rooms of n pieces (n>2),wherein a charge port of an m-th (1≦m≦(n−1)) treatment room is connectedto a discharge port of an m-th gas-heating unit, a charge port of ann-th treatment room is connected to a discharge port of an n-thgas-heating unit, a discharge port of the n-th treatment room isconnected to the heat exchanger, and a substrate is heated by gas heatedby the heating unit as a heating source.

By heating the treated substrate by heated gas, the substrate is heateduniformly without being influenced by material of formed matter on thetreated substrate. Thus, thermal treatment is possible withoutgenerating local distortion, and it is easy to achieve even thermaltreatment of breakable substrate such as glass by rapid heating.

By providing a preparatory heating room and a cooling room except thetreatment room performing thermal treatment, needless energy consumptionis reduced. That is, by charging cool (about room temperature) gassupplied from a gas-supplying unit to the cooling room, the substratehaving finished heat-treating is cooled. Thus, although temperature ofthe gas rises, thermal energy for heating gas is saved by supplying thegas to the gas-heating unit through the heat exchanger. By charging highgas in temperature discharged from the heat exchanger to the preparatoryheating room and heating the cooled (about room temperature) substrate,time for heating at the treatment room is shortened, and temperaturechange of heating gas is made small. Thus, thermal energy for gasheating is saved.

A method for heat-treating by the thermal treatment equipment comprisestreatment rooms of n pieces (n>2) performing heat-treating, apreparatory heating room, and a cooling room, and heating a substrateusing gas heated by heating units of n pieces as a heating source,wherein gas heated by an m-th (1≦m≦(n−1)) heating unit is supplied to anm-th treating room by treating rooms and gas-heating units of n pieces(n>2), gas supplied to the m-th treatment room is heated by an (m+1)-thheating unit and is supplied to an (m+1)-th treatment room, substratesarranged at the treatment room of n pieces are heated, gas supplied toan n-th treatment room is supplied to a heat exchanger, gas suppliedfrom a gas-supplying unit is used as a heating source for heating, gassupplied from the gas-supplying unit is supplied to the cooling room,gas discharged from the cooling room is supplied to a first gas-heatingunit through the heat exchanger, and gas discharged from the heatexchanger is supplied to the preparatory heating room.

By providing a preparatory room and a cooling room, time forheat-treating is shortened. By combining with batch type process systemtreating plural substrates in a lump, large quantity of substrates canbe treated efficiently.

For gas applied in the invention, inactive gas by nitrogen or noble gas,reducing gas of hydrogen, oxidizing gas of oxygen, dinitrogen monoxide,or nitrogen dioxide is used.

Using inactive gas by nitrogen or noble gas is applicable for thermaltreatment aiming at thermal treatment for crystallization of amorphoussemiconductor film, thermal treatment for gettering, andrecrystallization and activation after ion injection or ion doping(method injecting ion without separating mass).

By using hydrogen or hydrogen diluted by inert gas as reduction gas suchas hydrogen, hydrogen treating for compensating a defect ofsemiconductor (dangling bond) can be performed.

By using oxidizing gas such as oxygen, dinitrogen monoxide, and nitrogendioxide, oxide film can be formed at semiconductor substrate orsemiconductor film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a mode for carrying out of a thermaltreatment equipment applying for a method for heat-treating of theinvention:

FIG. 2 is a sectional view showing a mode for carrying out of thethermal treatment equipment applying for the method for heat-treating ofthe invention:

FIG. 3 is a layout view showing an example of the thermal treatmentequipment applying for the method for heat-treating of the invention:

FIG. 4 is a view describing an example of gas heating unit applicablefor the thermal treatment equipment of the invention;

FIG. 5 is a view describing an example of a heat exchanger applicablefor the thermal treatment equipment of the invention;

FIG. 6 is a graph describing change of substrate temperature atcrystallization process using method for heat-treating of the invention;

FIG. 7 is a graph describing change of substrate temperature atgettering process using method for heat-treating of the invention;

FIGS. 8A to 8F are sectional views describing process showing producingsemiconductor film applying the method for for heat-treating and thermaltreatment equipment of the invention: and

FIGS. 9A to 9F are sectional views describing process showing producingTFT applying the method for heat-treating and thermal treatmentequipment of the invention.

FIGS. 10A-10C are sectional views describing process showing producingan oxide film on a surface of a semiconductor applying the method forheat-treating and thermal treatment equipment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Modes for carrying out the invention will be described below referringfigures. FIG. 1 is a sectional view showing a mode for carrying out of athermal treatment equipment applying for method for heat-treating of theinvention. The thermal treatment equipment provides plural gas supplyingunits, plural gas heating units, plural treatment rooms and heatexchangers, a preparatory heating room, and a cooling room.

Gas supplied from a gas-supplying unit 107 is charged to the coolingroom. A substrate having finished heating process is arranged in thecooling room for certain period. The supplied gas contributes to fallingtemperature of the substrate, thereby temperature of the gas suppliedwith about room temperature rises. When there is not the substratehaving finished heating process, the gas passes through the room as itis.

The gas discharged from the cooling room passes through a thermalexchanger 108, and is supplied to a first gas-heating unit 111 a or 112a. The first gas-heating unit 111 a heats the gas at the predeterminedtemperature.

A discharge port of the second gas-heating unit 111 b is connected to acharge port provided at a first process room 101 a by a gas pipe, andthe heated gas is supplied. In the first process room 101 a, asubstrate-holding unit and shower plate blowing heated gas to thesubstrate are provided. Then, the supplied gas is discharged from thedischarge port provided at first process room 101 a by heating thesubstrate.

In order to prevent contamination from wall material at charging ofheated gas, the process room is formed using quartz or ceramic. As it isdifficult to form the process room with quartz meeting the size of thesubstrate when it is large, the process room may be applied with ceramicat its case. The structure of the holding unit is made as small aspossible in contact area with the substrate. The gas supplied to processroom 101 a is blown to the substrate passing through the shower plate.Small openings are formed at the shower plate at the predeterminedpitch, the heated gas is blown uniformly to the substrate. By providingthe shower plate, heating is performed uniformly even when area of thesubstrate is large.

Such the construction of the process room is similar as constructions ofa second process room 101 b, a third process room 101 c, a fourthprocess room 101 d, and a fifth process room 101 e.

The gas discharged from the first process room 101 a is used for heatingthe substrate again supplying to the second process room 101 b afterthat. Since temperature of the gas falls at the process, control isperformed so as to be the predetermined temperature by a secondgas-heating unit 111 b. The discharge port provided at the first processroom 101 a and the charge port of the second heating unit 111 b areconnected with a gas pipe, and the discharge port of the second heatingunit 111 b and the charge port provided at the second process room 101 bare connected with a gas pipe. These gas pipes may be provided with aheat insulation unit, though not shown.

Similarly, the heated gas supplied to the second process room 101 b issupplied to the third process room 101 c through a third gas heatingunit 111 c after used for heating the substrate. The heated gas suppliedto the third process room 101 c is supplied to the fourth process room101 d through a fourth gas heating unit 111 d after used for heating thesubstrate. The heated gas supplied to the fourth process room 101 d issupplied to the fifth process room 101 e through a fifth gas heatingunit 111 e after used for heating the substrate.

The gas discharged from the fifth process room 101 e is supplied to theheat exchanger 108 and used for heating gas supplied to the first gasheating unit 111 a from the cooling room 106. Further, after that, thegas is supplied to the preparatory heating room 105 and used for heatingthe substrate disposed therein.

The first to fifth process rooms are connected through gas heating unitsin a heat-treatment room 101 of FIG. 1. Construction of heat-treatmentrooms 102, 103, and 104 too is similar as the heat-treatment room 101.It is possible to perform thermal treatment different in heatingtemperature at every heat-treatment room by such the construction.Number of connecting is option without limiting to the above.

The substrates are set at treatment room every sheet. By connecting eachtreatment room with gas pipe in series and flowing the heated gascontinuously, quantity of the gas used and energy requiring for heatingcan be saved.

The heat exchanger 108 is provided for preheating gas supplying to thefirst gas-heating unit 111 a from the first gas-supplying unit 107previously. The gas can be heated previously by heat of the gasdischarged from each treatment room.

An example of the heat exchanger is shown in FIG. 5. A pipe where hightemperature gas flows therethrough and a fin as shown in the figure isprovided, and a pipe where cooled (about room temperature usually) gasflows therethrough and similarly a fin is provided are set up at theheat exchanger. Oil 403 is filled in a body of equipment 400 as a mediumtransmitting heat. The fin is provided for improvement of thermalexchange efficiency, and the high temperature gas transmits heat to theoil 403 and is discharged being made low temperature by such theconstruction. By the heat, low temperature gas is heated passing throughthe heat exchanger. Although a simple example of the heat exchanger isshown here, construction of heat exchanger applicable for thermaltreatment equipment of the invention may adopt another constructionwithout limiting to FIG. 5.

FIG. 4 shows an example of a construction of a gas heating unit. In FIG.4, a heat absorbing body 303 is provided at inside of a cylinder 301letting gas pass. For the heat absorbing body 303, high purity titaniumor tungsten, or matter formed by silicon carbide, quartz, or silicon isadopted. The cylinder 301 is formed by transparent quartz, and radiationof a light source 302 provided at outside of the cylinder heats the heatabsorbing body 303. Although the gas is heated contacting the heatabsorbing body 303, contamination is prevented by providing the lightsource at outside of the cylinder 301, and purity of passing gas can bekept. Inside of the body of equipment 300 may be evacuated so as toimprove heat insulation effect.

Next, an example of process of thermal treatment using the thermaltreatment equipment having the construction shown in FIG. 1 will bedescribed. The substrate arranged at the preparatory heating room 105 isheated to the predetermined temperature by the gas supplied from theheat exchanger 108. Heating temperature is possible to set to about 100to 450° C. For example, by heating to 450° C., dehydrogenation processof amorphous silicon film formed on the substrate is possible. Thesubstrate heated at a preparatory heating room 105 is moved to each oftreatment room 101 a to 101 e of the heat treatment room 101 andheat-treated there. The substrate is heated at the predeterminedtemperature by the first to fifth gas-heating units 111 a to 111 e.

After finishing thermal treatment of a certain time, the substrate ismoved to the cooling room 106. Gas supplied from the gas supplying unit107 and having temperature of about room temperature is supplied to thecooling room 106, thereby the substrate is cooled. Therefore, thesubstrate after thermal treatment arranged at the cooling room 106 canbe cooled rapidly. The gas absorbs heat of the substrate so as to riseto temperature higher than the room temperature. The gas is supplied tothe first heating unit 111 a after heated by the heat exchanger 108. Thesubstrate cooled to the predetermined temperature is collected.

By the preparatory heating room and the cooling room, it is possible toperform preparatory heating and cooling at the same time, thereby sheetsof treatment per unit time can be increased.

In order to save quantity of used gas and to improve thermal efficiency,it is desirable to make content volume of the treatment room as small aspossible. Size of inside of the treatment room is determined by size ofthe substrate and operating range of a transferring unit putting in andout the substrate. Although operating range of about 10 mm is requiredin order that the transferring unit puts in and out the substrate, sizeof one side of the treatment rooms is determined by thickness of thesubstrate and the minimum operating range of the transferring unit.

Although the method for heat-treating and the thermal treatmentequipment applying the method of the invention perform batch process asa premise, it is possible to raise temperature in comparatively shorttime to heat directly the treated substrate by heating gas and to lowertemperature rapidly by cooling the treated substrate of high temperaturestate by gas of about room temperature. Although attention is need whena weak substrate in thermal shock such as glass is used, it differs frominstant heating of several micro sec to several sec by light of a lampas the RTA of the related art, thereby the substrate is not damaged byrapid heating.

Gas used for heating or cooling can be selected by use of thermaltreatment. Using nitrogen or inert gas by noble gas is applicable forthermal treatment aiming at thermal treatment for crystallization ofamorphous semiconductor film, thermal treatment for gettering, andrecrystallization and activation after ion injection or ion doping(method injecting ion without separating mass). By using hydrogen orhydrogen diluted by inert gas, as reduction gas such as hydrogen,hydrogen treating for compensating a defect of semiconductor (danglingbond) can be performed. By using oxidizing gas such as oxygen,dinitrogen monoxide, and nitrogen dioxide, oxide film can be formed atsemiconductor substrate or semiconductor film.

The thermal treatment equipment applying the method for heat-treating ofthe above-mentioned invention can apply for various thermal treatment ofthe processed matter. For example, it is applied for thermal treatmentof semiconductor substrate forming an integrated circuit, thermaltreatment of an insulation substrate forming a TFT, and thermaltreatment of a metal substrate. For example, it is applied for thermaltreatment of a glass substrate forming a TFT. Even applying for not only600×720 mm but also 1200×1600 mm in the size of the substrate, thesubstrate can be heated uniformly. Further, it is needless to make thejig holding the substrate large.

EMBODIMENT MODE Embodiment 1

FIG. 2 shows an embodiment of thermal treatment equipment of theinvention. In FIG. 2, a first gas-heating unit 207 is providedcorresponding to a first treatment room 201, a second gas-heating unit208 is provided corresponding to a second treatment room 202, a thirdgas-heating unit 209 is provided corresponding to a third treatment room203, and a fourth gas-heating unit 210 is provided corresponding to afourth treatment room 204. A first gas-supplying unit 205, a secondgas-supplying unit 206, and a heat exchanger 211 are formed, and thesepipe arrangements have the similar construction as the thermal treatmentequipment described in the mode for carrying out.

The first gas-supplying unit 205 supplies heating gas to the heatexchanger 211 here through a cooling room not shown. The gas dischargedfrom the heat exchanger 211 is supplied to a preparatory heating roomnot shown.

Substrates 215 held by a cassette 214 are transferred to each treatmentroom by a transferring unit 213, and are set on a holding unit 216. Eachtreatment room puts in and out the substrate by opening/closing of agate valve.

FIG. 3 shows a construction of a thermal treatment equipment providingplural treatment rooms. Heat treatment rooms 501 and 502, firstgas-supplying units 506 and 509, second gas-supplying unit 507 and 510and gas-heating units 508 and 511 are provided. The heat treatment rooms501 and 502 are piled in plural stages, and gas-heating units areprovided corresponding to the room. Such the construction may bereferred to FIG. 2. A preparatory heating room 520 and a cooling room530 are arranged longitudinally between the heat treatment rooms 501 and502. Cassettes 505 a to 505 c are applied for holding and transferringthe substrate. The substrate is used for moving through the cassettes505 a to 505 c, the heat treatment rooms 501 and 502, the preparatoryheating room 520, and the cooling room 530 by the transferring unit 504.

Number of stages of the treatment room is determined by time for thermaltreatment and operation speed of the transferring unit (that is, ablespeed to move the substrate). When tact time is about 10 minutes, threeto ten stages are set for the heat treatment rooms 501 and 502.

Although FIG. 3 shows an example of the construction of the thermaltreatment equipment by large quantity batch process system, it ispossible to take any arrangement of others without limiting to theconstruction and the arrangement. Since the thermal treatment equipmentshown in the embodiment is a batch process system and a system heatingthe treated substrate by heated gas, thermal treatment is performeduniformly even when size of the substrate is large. For example, it isapplicable even for thermal treatment of the substrate longer than 1000mm in length of one side.

Characteristic of method for heat-treating and the thermal treatmentequipment using the method of the invention is to have no limitation ofa shape of the treated substrate or a size. A strong suscepter isneedless by sheet process even when the treated substrate is large,thereby making small can be designed for the size. A large scale heatingunit is needless so as to save power consumption.

Embodiment 2

An example of thermal treatment accompanied by crystallization ofsemiconductor film and gettering using method for heat-treating and thethermal treatment equipment applying the method of the invention will bedescribed using FIGS. 8A to 8F.

Although material of a substrate 600 is not limited especially in FIG.8A, barium borosilicate glass, alminoborosilicate glass, or quartz aredesirably used for the material. An inorganic insulation film of 10 to200 nm thickness is formed at the surface of the substrate 600 for ablocking layer 601. An example of the suitable blocking layer is asilicon oxide nitride film produced by plasma CVD method, and a matterforming a first silicon oxide nitride film produced by SiH₄, NH₃, andN₂O in 50 nm thickness and forming a second silicon oxide nitride filmproduced by SiH₄ and N₂O in 100 nm thickness is used. The blocking layer601 is provided so that alkali metal included in the glass substratedoes not diffuse into semiconductor film forming at an upper layerthereof, and it is possible to omit at the case of a substrate ofquartz.

For a semiconductor film (a first semiconductor film) 602 havingamorphous structure forming on the blocking layer 601, semiconductormaterial having silicon for its main ingredients is used. Typically,amorphous silicon film or amorphous silicon germanium film is applied,and it is formed to 10 to 100 nm thickness by plasma CVD method,decompression CVD method, or sputtering method. In order to obtain goodcrystal, impurity concentration of oxygen and nitrogen included in thesemiconductor film 602 having amorphous structure may be reduced lessthan 5×10¹⁸/cm³. These impurities cause to disturb crystallization ofamorphous semiconductor and to increase density of trapping center orrecombination center even after crystallization. Because of that, it isdesirable not only to use gas of high impurity material but also to usea CVD equipment for ultra high vacuum providing mirror process(electropolishing process) in the reaction room or evacuation system ofoil free.

After that, a metal element having catalysis promoting crystallizationis added to surface of the semiconductor film 602 having amorphousstructure. Metal elements having catalysis promoting crystallization ofthe semiconductor film are ferrous (Fe), nickel (Ni), cobalt (Co),ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir),platinum (Pt), copper (Cu), gold (Au), etc. and one kind or plural kindselected from them is used. Typically, using nickel, nickel acetatesolution including nickel of 1 to 100 ppm converted into weight isapplied by a spinner so as to form a catalyst content layer 603. Themore content quantity of nickel is, in the shorter time crystallizationcan be performed.

In this case, in order to adapt the solution, a very thin oxide film isformed by ozone content solution as a surface process of thesemiconductor film 602 having amorphous structure, clean surface isformed by etching the oxide film with mixed liquor of hydrofluoric acidand hydrogen peroxide water, after that, a very thin oxide film isformed by processing again with the ozone content solution. Sincesurface of the semiconductor film such as silicon is originallyhydrophobic, nickel acetate solution can be applied uniformly by formingthe oxide film like this.

The catalyst content layer 603 may be formed by sputtering method,deposition method, and plasma process without limiting such the method.The catalyst content layer 603 may be formed before forming thesemiconductor film 602 having amorphous structure, that is, on theblocking layer 601.

Thermal treatment for crystallization is performed while keeping statecontacting the semiconductor film 602 having amorphous structure and thecatalysis content layer 603. The thermal treatment equipment shown inFIG. 1 is used for the thermal treatment. FIG. 6 is a graph describingprocess of the thermal treatment, and process of the thermal treatmentwill be described below referring the graph.

Nitrogen and argon are used for heating gas. The substrate 600 formingamorphous semiconductor film is moved to a preparatory heating room froma cassette by a transferring unit, and is heated previously to thepredetermined temperature. After that, moving the substrate to atreatment room, a gate valve is closed. After closing the gate valve,letting heated nitrogen flow and filling, in a reaction room withnitrogen, the substrate is heated.

Increasing quantity of flow of nitrogen, nitrogen gas supplied by agas-heating unit is heated to first temperature. The heating temperaturecan be adjusted by electric power supplying to a heating element orsupplying quantity of the power and nitrogen. Here, setting to 550±50°C. as the first temperature, the substrate is heated (step of risingtemperature 1 shown in FIG. 6). Necessary time for rising to thetemperature is only two minutes.

When temperature of the substrate becomes the first temperature, thestate is kept for three minutes. At this step, crystal nucleus is formedat amorphous semiconductor film (step of forming nucleus shown in FIG.6). After that, the substrate is heated to second temperature forcrystallization. Raising temperature of nitrogen gas for heating to675±25° C., the substrate is heated (step of rising temperature 2 shownin FIG. 6). When temperature of the substrate becomes the secondtemperature, keeping the temperature for five minutes, crystallizationis performed (step of crystallization shown in FIG. 6). Of course,nitrogen gas for heating is continued to supply.

After the predetermined time, supply of nitrogen gas for heating isstopped, and nitrogen gas for cooling is supplied. The gas may benitrogen gas having room temperature. Then the substrate is cooledrapidly (step of falling temperature shown in FIG. 6). The time is aboutthree minutes. After cooling the substrate to 300° C,. the substrate isput out from the treatment room by the transferring unit, and is movedto the cooling room. Here, the substrate is further cooled to less than150° C. (step of transfer shown in FIG. 6). After that, by transferringthe substrate to the cassette, thermal treatment for crystallization isfinished.

Time for putting the substrate in the thermal treatment equipment andputting it out after heat-treating is 13 minutes. Thus, by using thethermal treatment equipment and the method for heat-treating of theinvention, thermal treatment for crystallization can be performed invery short time.

Thus, a semiconductor film (first semiconductor film) 604 having crystalstructure shown in FIG. 8B can be obtained.

Further, in order to raise crystallinity (rate of crystal component towhole volume of the film) and to repair defect remained in crystalgrain, it is effective too to radiate laser beam to the semiconductorfilm 604 having crystal structure as shown in FIG. 8C. Excimer laserbeam less 400 nm wavelength, and a second and third harmonics of YAGlaser are used for the laser. About any lasers, laser process to thesemiconductor film 604 having crystal structure may be performed withoverlap rate of 90 to 95% by using pulse laser beam of about 10 to 1000Hz frequency and gathering the laser beams to 100 to 400 mJ/cm² byoptical system.

In the semiconductor film (first semiconductor film) 605 having thecrystal structure obtained by such the way, catalyst element (nickelhere) is remained. It is remained in concentration more than 1×10¹⁹/cm³as average concentration though it is not distributed uniformly in thefilm. Although various kinds of semiconductor elements, from TFT down,is possible to form in any state, the element is removed by getteringusing the following method.

First, a thin barrier layer 606 is formed at surface of thesemiconductor film 605 having the crystal structure as shown in FIG. 8D.Although thickness of the barrier layer is not especially limited,chemical oxide formed by processing simply with ozone water may besubstituted for the barrier layer. By processing by aqueous solutionmixing sulfuric acid, hydrochloric acid, and nitric acid and hydrogenperoxide, similarly the chemical oxide can be formed. As another method,plasma process in oxide atmosphere and oxide process generating ozone byultraviolet irradiation in oxygen content atmosphere may be performed.Thin oxide film is formed heating about 200 to 350° C. using a cleanoven so as to form a barrier. Oxide film of about 1 to 5 nm may bedeposited by plasma CVD method, sputtering method, and deposition methodso as to form a barrier layer.

On the barrier layer, a semiconductor film (second semiconductor film)607 is formed to 25 to 250 nm thickness by plasma CVD method orsputtering method. Typically, amorphous silicon film is selected. Sincethe semiconductor film 607 is removed later, it is desirable to form lowfilm in density because selecting ratio of etching to the semiconductorfilm 605 having crystal structure is raised. For example, at forming theamorphous silicon film by plasma CVD method, temperature of thesubstrate is set to 100 to 200° C., and hydrogen of 25 to 40 atomicpercent is included in the film. It is similar at adopting sputteringmethod, temperature of the substrate is set less than 200° C., and alarge quantity of hydrogen is included in the film by sputtering withmixed gas of argon and hydrogen. Noble gas element can be taken in thefilm at the same time by adding the noble gas element at forming film bysputtering method or plasma CVD method. By the noble gas element takenin such the way too, gettering site can be formed.

After that, the noble gas element is added to the semiconductor film 607so as to include with density of 1×10²⁰ to 2.5×10²²/cm³ by the iondoping method or the ion injection method. Although accelerating voltageis option, ion of the noble gas element injected because of the noblegas element passes through the semiconductor film 607 and the barrierlayer 606, and a part of ion may reach the semiconductor film 605 havingcrystal structure. Since the noble gas element is inactive itself insemiconductor film, the gas does not very influence elementcharacteristic even at area including with density of about 1×10¹³ to1×10²⁰/cm³ close surface of the semiconductor film 605. The noble gaselement may be added at step forming the semiconductor film 607.

For the noble gas element, one kind or plural kinds selected from helium(He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) is used. Thenoble gas element is used as ion source to form gettering site in theinvention, and the gas is injected to the semiconductor film by iondoping method or ion injection method. Injecting ion of these noble gaselements has two meanings. One is to give distortion to thesemiconductor by forming dangling bond using injection, and the other isto give distortion by injecting the ion between lattices of thesemiconductor. Although ion injection of inactive gas satisfies the bothat the same time, especially the latter one is obtained clearly whenlarger element in atomic radius than silicon such as argon (Ar), krypton(Kr), and xenon (Xe).

In order to achieve gettering surely, it is necessary to perform thermaltreatment after that. FIG. 7 is a graph describing the process ofthermal treatment, and the process of the thermal treatment will bedescribed referring the graph. For the thermal treatment, the thermaltreatment equipment of the invention is used similarly. It is desirableto use the equipment constructed like FIG. 5 in order to treat manysubstrates efficiently. Nitrogen and argon are used for heating gas.

The substrate 600 forming the construction of FIG. 8D is set in thereaction pipe from the cassette by the transferring unit, and afterthat, the gate valve is closed. During the time, it is considered thatnitrogen is continued to supply from the gas-supplying unit in thereaction pipe and mixture of the air is made the minimum. After closingthe gate valve, flowing quantity of the nitrogen is increased so as tosubstitute filling with nitrogen in the reaction pipe.

Then, increasing the flowing quantity of the nitrogen, nitrogen gassupplied by the gas-heating unit is heated to third temperature. Theheating temperature can be adjusted by electric power supplying to aheating element or the power and supplying quantity of nitrogen. Here,setting to 675±25° C. as the third temperature, the substrate is heated(step of rising temperature shown in FIG. 7). Necessary time for raisingto the temperature is two minutes.

When temperature of the substrate becomes the third temperature, thestate is kept for three minutes. Thus, gettering is formed (step ofgettering shown in FIG. 7). In the gettering, a catalyst element at agot area (getting site) is discharged by thermal energy and moves togettering site by diffusion. Therefore, the gettering depends on processtemperature, and for the shorter time the gettering advances at thehigher temperature. Direction that catalyst element moves is distance ofabout thickness of the semiconductor film as shown with the arrow inFIG. 8E, and gettering is finished completely in comparatively shorttime.

After the predetermined time, supply of nitrogen gas for heating isstopped, and nitrogen gas for cooling is supplied. The gas may benitrogen gas having room temperature. Then the substrate is cooledrapidly (step of falling temperature shown in FIG. 7). The time is aboutthree minutes. After cooling the substrate to 300° C., the substrate isput out from the treatment room by the transferring unit, and is movedto a buffer cassette. Here, the substrate is further cooled to less than150° C. (step of transfer shown in FIG. 7). After that, by transferringthe substrate to the cassette, thermal treatment for gettering isfinished.

Time from putting the substrate in the thermal treatment equipment toputting it out after heat-treating is 9 minutes. Thus, by using thethermal treatment equipment and the method for heat-treating of theinvention, thermal treatment for gettering can be performed in veryshort time.

Even in the thermal treatment, the semiconductor film 607 includingnoble gas element with density of more than 1×10²⁰/cm³ does notcrystallize. This is considered that the noble gas element remains inthe film without being re-discharged even in the range of theabove-mentioned treating temperature and blocks crystallization of thesemiconductor film.

After that, the amorphous semiconductor 607 is removed by etchingselectively. Using dry etching by CIF₃ not using plasma or aqueoussolution including density of 20 to 30%, desirably 25%, of hydrazine ortetraethyl-ammonium-hydro-oxide (chemical formula (CH₃)₄NOH) as etchingmethod, the semiconductor can be easily removed by heating to 50° C. Atthis time, the barrier layer 606 functions as an etching stopper, andremains without almost being etched. The barrier layer 606 may beremoved by hydrofluoric acid after that.

Thus, a semiconductor film 608 having crystal structure where density ofcatalyst element is reduced to less than 1×10¹⁷/cm³ can be obtained asshown in FIG. 8F. The semiconductor film 608 having crystal structureformed by such the way is formed as a thin bar or a thin flat bar typecrystal by effect of catalyst element, and each crystal grows to aparticular direction macroscopically. The semiconductor film 608 havingsuch the crystal structure is applied not only for the active layer ofTFT but also for a photoelectric transfer layer of photo sensor andsolar battery.

Embodiment 3

A method producing a TFT using the semiconductor film produced byEmbodiment 2 will be described referring FIG. 9. In the processproducing the TFT described in the embodiment, the method forheat-treating and the thermal treatment equipment of the invention isused.

First, in FIG. 9A, semiconductor films 702 and 703 separated in islandshape are formed on a transparent substrate 700 made ofalumino-borosilcate glass or barium-borosilicate glass by thesemiconductor film produced in Embodiment 2. A first insulation film 701of 50 to 200 nm thickness combined with one or plural kind selected fromsilicon nitride, silicon oxide, and silicon nitride oxide is formedbetween the substrate 700 and the semiconductor film.

After that, a second insulation film 704 of 80 nm thickness is formed asshown in FIG. 9B. The second insulation film 704 is used as a gateinsulation film and is formed using plasma CVD method or sputteringmethod. Silicon oxide nitride film produced by adding O₂ to SiH₄ and N₂Ois possible to reduce fixed density of electric charge in the film forsecond insulation film 704, it is desirable for the gate insulationfilm. Insulation film such as silicon oxide film and tantalum oxide filmmay be used for the gate insulation film as single layer or laminatinglayer structure without limiting to such the silicon oxide nitride film.

A first conductive film for forming a gate electrode on the secondinsulation film 704 is formed. Although there is no limitation of kindof the first conductive film, conductive material such as aluminum,tantalum, titanium, tungsten, and molybdenum or alloy of them areapplied. For the structure of the gate electrode using such thematerial, laminating structure of tantalum nitride or titanium nitride,and tungsten or molybdenum tungsten alloy, and laminating structure oftungsten, and aluminum or copper are adopted. At using aluminum, matteradded with titanium, scandium, neodymium, silicon, and copper of 0.1 to7 weight % is used in order to raise heat resistance. The firstconductive film of 300 nm thickness is formed.

After that, forming a resist pattern, gate electrodes 705 and 706 areformed. Wiring connecting to the gate electrodes is formed at the sametime though it is not shown.

Masking the gate electrodes, an n type semiconductor domain is formedwith self-matching as shown in FIG. 9C. Phosphorus is injected by ioninjecting method or ion doping method (here, method injecting ion notseparating mass) in doping. Phosphorus density of the domain is setwithin the range of 1×10²⁰ to 1×10²¹/cm³.

Next, a mask 709 covering one of the semiconductor films 703 is formed,and a p type semiconductor domain 710 is formed on the semiconductorfilm 702 as shown in FIG. 9D. Boron is used for adding impurity, and isadded with density of 1.5 to 3 times as much as phosphorus in order toinvert n type. Phosphorus density of the domain is set within the rangeof 1.5×10²⁰ to 3×10²¹/cm³.

After that, a third insulation film 711 of 50 nm thickness made ofsilicon oxide nitride film or silicon nitride film is formed by plasmaCVD method as shown in FIG. 9E.

Then, recovery of crystallization of n type and p type semiconductordomains and thermal treatment for activation are performed. The thermaltreatment is performed similarly as FIG. 7 of Embodiment 2. Fourthtemperature suitable for the activation is set to 450±50° C., andthermal treatment of 1 to 10 minutes may be performed.

Nitrogen and argon are used for heating gas. Thermal treatment of threeminute is performed heating gas to temperature of 500° C. foractivation. The gas may be reducing atmosphere added to the gas withhydrogen. Hydrogenation can be performed at the same time by addedhydrogen.

The substrate is moved to a preparatory heating room from a cassette bya transferring unit, and is heated previously to the predeterminedtemperature. After that, moving the substrate to a treatment room, agate valve is closed. After closing the gate valve, letting heatednitrogen flow and filling in a reaction room with nitrogen, thesubstrate is heated. Time from putting the substrate in the treatmentroom to putting it out after heat-treating is about 8 to 9 minutessupposing 2 minutes for rising temperature and 3 minutes for cooling.Thus, by using the thermal treatment equipment and the method forheat-treating of the invention, thermal treatment for activation can beperformed in very short time.

When thermal treatment by RTA method is performed at the state forminggate electrodes on a glass substrate, the glass substrate is possiblydamaged because the gate electrodes absorb selectively radiation oflight of lamp and the substrate is heated. The thermal treatmentaccording to the invention is not influenced because of heating by gas.

A fourth insulation film 712 shown in FIG. 9F is formed of silicon oxidefilm and silicon oxide nitride. The insulation film may be formed byorganic insulation material such as polyimide or acryl, and surfacethereof may be flattened.

Next, a contact hole reaching impurity domain of each semiconductor filmfrom surface of the fourth insulation film 712 is formed, and wiring isformed using Al, Ti, and Ta. In FIG. 9F, symbols 713 and 714 function asa source wire or a drain electrode. Thus, an n channel type TFT and a pchannel type TFT are formed. Although each TFT is shown as a simplesubstance, a CMOS circuit, an NMOS circuit, and a PMOS circuit areformed using these TFTs.

Embodiment 4

It is possible to form an oxide film on the surface of a semiconductorby mixing an inert gas for heating with a gas selected from the groupconsisting of oxygen, nitrous oxide, and nitrogen dioxide, and usingthis as an oxidizing gas in a heat treatment method, and a heattreatment apparatus applying the heat treatment method, of the presentinvention.

FIGS. 10A to 10C show such an example, and between 1 and 30% of oxygenis mixed with nitrogen used as a heating gas. By performing heattreatment at a temperature of 700 to 850° C., a field oxide film forelement separation, and a gate insulating film can be formed on a singlecrystal silicon substrate.

An n-well 802 and a p-well 803 are formed in a substrate 801 made fromsingle crystal silicon having a relatively high resistance (for example,n-type, on the order of 10 Ωcm) in FIG. 10A. Next, a field oxide film805 is formed using the heat treatment method of the present inventionand using a mixed gas of oxygen and nitrogen as a heating gas. Boron (B)may be introduced into the semiconductor substrate by selective ioninjection of boron at this point to form a channel stopper. The heattreatment temperature is set from 700 to 850° C.

Formation of a silicon oxide film 806 that becomes a gate insulatingfilm is then similarly performed. An apparatus having the structureshown by FIG. 1 may be used as the apparatus employed in forming thefield oxide film 805 and the silicon oxide film 806.

Next, as shown by FIG. 10B, a polycrystalline silicon film used forgates is formed having a thickness of 100 to 300 nm using CVD. Thepolycrystalline silicon film used for gates may be doped in advance byphosphorous (P) having a concentration on the order of 10²¹/cm³ in orderto lower its resistance, and a strong n-type impurity may also bediffused after forming the polycrystalline silicon film. A silicide filmis formed having a thickness of 50 to 300 nm here on thispolycrystalline silicon film in order to additionally lower theresistance. It is possible to apply materials such as molybdenumsilicide (MoSix), tungsten silicide (WSix), tantalum silicide (TaSix),and titanium silicide (TiSix) as the silicide material, and the film maybe formed in accordance with a known method. The polycrystalline siliconfilm and the silicide film are then etched, forming gates 807 and 808.The gates 807 and 808 have a two-layer structure from polycrystallinesilicon films 807 a and 808 a, and silicide films 807 b and 808 b,respectively.

Source and drain regions 820 of an n-channel MOS transistor, and sourceand drain regions 821 of a p-channel MOS transistor are then formed asshown in FIG. 10C by ion injection. The heat treatment method and theheat treatment apparatus of the present invention can of course be usedin order to perform recrystallization and activation of these sourcesand drain regions. The heat treatment temperature is set from 700 to850° C., preferably so as to become 850° C., and heat treatment isperformed by a heat treatment means and employing the gas used forheating. Impurities can be activated, and the source and drain regionscan be made lower resistance by this heat treatment process.

An n-channel MOS transistor 831 and a p-channel MOS transistor 830 canthus be completed. The structure of the transistors explained inEmbodiment mode is only one example, and it is not necessary to placelimitations on the manufacturing processes and the structures shown inFIGS. 10A to 10C. CMOS circuits, NMOS circuits, and PMOS circuits can beformed using these transistors. Further, it is possible to form varioustypes of circuits, such as shift registers, buffers, sampling circuits.D/A converters, and latches by using the transistors, and semiconductordevices such as memories, CPUs, gate arrays, and RISC processors can bemanufactured. High-speed operation is possible for these circuits due tothe MOS structure, and further, they can be made to have lower electricpower consumption by using a driver voltage from 3 to 5 V.

As described above, according to the invention, a strong suscepter isneedless by sheet process even when the treated substrate is large,making small can be designed for the size without limitation of a shapeof the treated substrate or a size. Since the method for heat-treatingand the thermal treatment equipment applying the method of the inventionis a batch process system and a system heating the treated substrate byheated gas, thermal treatment is performed uniformly even when size ofthe substrate is large, and it is applicable even for thermal treatmentof the substrate longer than 1000 mm in length of one side. A largescale heating unit for the substrate is needless. By providing thepreparatory heating room and the cooling room, preparatory heating andcooling are possible to perform at the same time, thereby number ofsheets treated per unit time is increased.

The method for heat-treating of the invention can apply for thermaltreatment of semiconductor substrate forming an integrated circuit,thermal treatment of an insulation substrate forming a TFT, and thermaltreatment of a metal substrate. For example, it is applied for thermaltreatment of a large size mother glass substrate forming a TFT. It isneedless to make the jig holding the substrate large. Further,crystallization of the amorphous semiconductor film, gettering,activation of impurity, hydrogenation, and oxidation of semiconductorsurface are performed in short time. Such the processes can be taken inmanufacturing process of the semiconductor element.

1. A method for manufacturing a semiconductor device comprising thesteps of: forming a semiconductor film over a substrate; introducing acrystallization promoting material to the semiconductor film; applying afirst gas to the semiconductor film in a first room to heat thesemiconductor film; applying a second gas to the semiconductor film in asecond room to crystal the semiconductor film after applying the firstgas; applying a third gas to the crystalline semiconductor film in athird room to cool the crystalline semiconductor film, and gettering thecrystallization promoting material from the crystalline semiconductorfilm, wherein a temperature of the first gas is higher than atemperature of the third gas, and wherein a temperature of the secondgas is higher than the temperature of the first gas.
 2. A methodaccording to claim 1, wherein the first gas comprises at least one ofnitrogen and a noble gas.
 3. A method according to claim 1, wherein thethird gas comprises at least one of nitrogen and a noble gas.
 4. Amethod according to claim 1, wherein the crystallization promotingmaterial comprises at least one material selected from the groupconsisting of Ni, Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au.
 5. A methodfor manufacturing a semiconductor device comprising the steps of:forming a semiconductor film over a substrate; introducing acrystallization promoting material to the semiconductor film; applying afirst gas to the semiconductor film in a first room to heat thesemiconductor film; applying a second gas to the semiconductor film in asecond room to crystal the semiconductor film after applying the firstgas; applying a third gas to the crystalline semiconductor film in athird room to cool the crystalline semiconductor film, forming aninsulating film on the crystalline semiconductor film; forming anamorphous semiconductor film on the insulating film; and applying afourth gas to the crystallization semiconductor film to getter thecrystallization promoting material from the crystalline semiconductorfilm thereby the crystallization promoting material diffuses into theamorphous semiconductor film though the insulating film, wherein atemperature of the first gas is higher than a temperature of the thirdgas, and wherein a temperature of the second gas is higher than thetemperature of the first gas.
 6. A method according to claim 5, whereinthe first gas comprises at least one of nitrogen and a noble gas.
 7. Amethod according to claim 5, wherein the third gas comprises at leastone of nitrogen and a noble gas.
 8. A method according to claim 5,wherein the second gas comprises at least one of nitrogen and a noblegas.
 9. A method according to claim 5, wherein the crystallizationpromoting material comprises at least one material selected from thegroup consisting of Ni, Fe, Co, Ru, Rh, Pd, Os, Ir, Pt, Cu and Au.
 10. Amethod for manufacturing a semiconductor device comprising the steps of:forming a semiconductor film over a substrate; introducing acrystallization promoting material to the semiconductor film; applying afirst gas to the semiconductor film in a preparatory heating room toheat the semiconductor film; applying a second gas to the semiconductorfilm in a process room to crystal the semiconductor film after applyingthe first gas; applying a third gas to the crystalline semiconductorfilm in the process room to cool the crystalline semiconductor film;applying a fourth gas to the crystalline semiconductor film in a coolingroom to cool the crystalline semiconductor film; and applying a fifthgas to the crystalline semiconductor film to getter the crystallizationpromoting material from the crystalline semiconductor film, wherein atemperature of the first gas is higher than a temperature of the fourthgas, and wherein a temperature of the second gas and a temperature ofthe fifth gas are higher than the temperature of the first gas and atemperature of the fourth gas.
 11. A method according to claim 10,wherein the first gas comprises at least one of nitrogen and a noblegas.
 12. A method according to claim 10, wherein the third gas comprisesat least one of nitrogen and a noble gas.
 13. A method according toclaim 10, wherein the crystallization promoting material comprises atleast one material selected from the group consisting of Ni, Fe, Co, Ru,Rh, Pd, Os, Ir, Pt, Cu and Au.